Heretofore, as the autographic ink or jet printing ink used for recording on materials to be recorded (e.g. paper, etc.), a solution or dispersion in which various dyes or pigments are dissolved or dispersed has been employed.
A pigment-dispersed type ink has such an advantage that it is superior in durability (e.g. light resistance, etc.). However, dispersion processing in which the pigment is sufficiently dispersed in this ink is required in order to prevent the pigment from precipitating or aggregating with time.
On the other hand, an oil ink or aqueous ink in which the dye is dissolved is advantageously used in comparison with the pigment because no troublesome dispersion processing is required.
However, in this kind of ink or dye concentrated solution, no denaturation or precipitation of the dye with time is required.
As the dye which satisfies such a requirement, for example, a salt-forming type basic and acidic dye, in which a basic dye is treated with a fatty acid, metal complex-containing dye having a water-soluble group (e.g. sulfonic group, etc.), in which an acidic dye is treated with an organic amine and the like are known.
However, a conventional oil ink in which an oil-soluble or alcohol-soluble dye is dissolved in a polar organic solvent is denaturated by environmental change (e.g. temperature, humidity change, etc.). Particularly, it is liable to absorb water in the atmosphere and is inferior in storage stability, which results in deterioration of the quality of the product.
Further, as the method for preparing a liquid composition of an anion type dye (e.g. aqueous ink, recording solution for jet printing, etc.), various methods have been suggested. Among the anion type dye, a direct dye, particularly black dye is generally inferior in water solubility and these dyes have an amino group in a dye molecular structure without exception. Therefore, when a liquid composition of these dyes is stored for a long period of time, deterioration due to oxidation is caused, which results in an increase of viscosity, decrease of concentration and formation of precipitation. Accordingly, the improvement of these disadvantages is desired.
Under these circumstances, the present inventors have studied intensively. As a result, it has been found that, by treating an azo water-soluble dye having a phosphonic acid group and sulfonic acid group in a dye molecular structure with a specific amine, a dye wherein the sulfonic acid group is preferentially or selectively salt-formed can be obtained and the-salt-formed dye has excellent solubility to a hydrophilic organic solvent having low toxicity, or to an oil liquid solvent which may contain water, and the present invention has been completed.